This invention is in the field of optical particle counters. This invention relates generally to an optical particle counter capable of spatially resolving electromagnetic radiation scattered off of or emitted by particles. This invention also relates to methods for detecting and sizing particles and methods for spatially resolving an interaction of particles with a beam of electromagnetic radiation
A large portion of the micro-contamination industry is reliant on the use of particle counters, such as are described in a large number of U.S. patents, including U.S. Pat. Nos. 3,851,169, 4,348,111, 4,957,363, 5,085,500, 5,121,988, 5,467,188, 5,642,193, 5,864,399, 5,920,388, 5,946,092, and 7,053,783. U.S. Pat. Nos. 4,728,190, 6,859,277, and 7,030,980, 5,282,151 also disclose particle counters and are hereby incorporated by reference in their entirety. Aerosol particle counters are often used to measure air-born particle contamination in clean-rooms and clean zones. Liquid phase particle counters are often used to measure particulate contamination in the water treatment and chemical processing industries.
Particle counters capable of spatially resolving electromagnetic radiation scattered or emitted by particles typically employ two-dimensional detectors, such as the particle detector described in U.S. Pat. No. 5,282,151. U.S. Pat. No. 7,170,601 and U.S. Patent Application Publication No. US 2006/0001874 A1 also disclose a particle counter capable of spatially resolving electromagnetic radiation scattered or emitted by particles. These optical particle counters collect scattered or emitted electromagnetic radiation in a direction parallel to the fluid flow direction and are capable of spatially resolving the source of scattered or emitted electromagnetic radiation along directions perpendicular to the fluid flow direction. These particle counters, however, lack the ability to spatially resolve scattered or emitted electromagnetic radiation in a direction parallel to the fluid flow direction. The particle detection systems described herein utilize a geometrical configuration which allows for spatially resolving electromagnetic radiation scattered or emitted by particles in directions parallel to the fluid flow direction as well as perpendicular to the fluid flow direction.